As a method for manufacturing a so-called seamless capsule, there has been known a method wherein a liquid filler is flown out of the central nozzle of a multiple nozzle, a liquid capsule shell material is simultaneously flown out of an annular nozzle surrounding the central nozzle, and they are cut to drop into a cooling liquid (curing liquid). In this method, a droplet is dropped in the cooling liquid to change into a spherical shape, and then the shell material is gelled to stabilize the spherical shape.
A seamless capsule having an aspherical shape such as an elliptic shape, an oval shape, and a both side evenly convex spherical shape as seen in a popular capsule is desired from the viewpoints of easy taking, simple treating or product differentiation.
Conventionally, some methods have been proposed. For example, the methods are a method in which the spherical seamless capsule obtained by the above method is reformed into an aspherical shape through a proper forming device before drying the capsule, and a method in which the spherical seamless capsule is heated to convert its capsule shell membrane from a gel state to a sol sate before drying, and is formed into an aspherical shape through a proper forming device, and the aspherical seamless capsule thus obtained is then cooled to gel the shell membrane to stabilize the shape followed by drying, as described in JP Application Laid-Open No. 2000-325431.
However, the conventional methods for manufacturing an aspherical seamless capsule mentioned above have problems as follows.
In the former method, the spherical seamless capsule, whose shell membrane has a high percentage of water content and so is highly elastic before drying, is likely to return into its original spherical shape. Also, this method has a problem that it takes a long time to form into the aspherical shape because of a long stress relaxation time.
The latter method, described in JP Application Laid-Open No. 2000-325431, takes a relatively short time to form into an aspherical shape. However, the gelled spherical seamless capsule, which has a high percentage of water content before drying, is heated to convert to the sol with remarkable changes in physical properties caused by a sol/gel transformation. Therefore, the method has a problem that the seamless capsule is difficult to treat and requires a strict temperature control. Both of the methods described above also have a problem that the seamless capsule formed into an aspherical shape is dried to cause the shell membrane to shrink, resulting in wrinkles on the membrane surface and variation in shape.
The object of the present invention is to provide a method and an apparatus for manufacturing an aspherical seamless capsule to solve the problems described above.